Sparks From Workman's Hammer Ignited Deadly Mendocino Ranch Fire

SACRAMENTO (CBS SF) -- The deadly Ranch Fire that burned through Colusa, Glenn, Lake and Mendocino counties last July, the largest wildfire in California history, was ignited by sparks from a workman's hammer, Cal Fire officials announced Thursday.

The fire, which erupted on July 27, 2018, burned a total of 410,203 acres, destroyed 280 structures and resulted in one firefighter's death and other three firefighters being injured.

Cal Fire investigators were immediately dispatched to the fire and began working to determine the origin and cause of the blaze. After a meticulous and thorough investigation, it has been determined that the blaze was caused by a spark or hot metal fragment from a hammer driving a 24-inch metal concrete stake into the ground.

Officials did not identify who was responsible and said no charges have been filed.

The fire started early afternoon north of the community of Upper Lake in tinder dry vegetation, strong winds, low humidity and hot temperatures. Those conditions caused the fire to spread quickly.

The Ranch Fire was one of the two fires that made up the Mendocino Complex. The other fire in the Mendocino Complex was the River Fire. Total acreage burned by the two combined fires of the Mendocino Complex was 459,123 acres.